This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Increasing scientific and industrial effort is focused on the development of closed-loop systems (artificial pancreas) to control glucose metabolism in people with diabetes, particularly T1DM. Experiments are being conducted with CGM coupled with insulin pumps and a control algorithm. While such systems have proven feasible in steady metabolic states, they fail during changing metabolic demands, such as meals and physical activity. In order to account for such metabolic disturbances we have developed and tested in silico a new closed-loop control algorithm, which uses individual parameters of insulin sensitivity and heart rate. The proposed pilot trial will test this algorithm in vivo with T1DM patients who use insulin pumps to maintain glycemic control. Changes in heart rate will be used as a correlate to increased metabolic demand. If successful, this study will establish the following paradigm: instead of approaching a person "blindly" with a generic control algorithm, an initial test (e.g. oral glucose tolerance test) would allow setting individual parameters, which then will be used to initialize closed-loop control. This approach has the potential to overcome some of the current limitations of closed-loop control, particularly its inability to account for the highly idiosyncratic reaction of a person to metabolic disturbances, such as meals and physical activity.